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14.SWEEP
MULTIPLICATION
(MAGNIFI-
CATION)
The apparent magnification of the delayed sweep is deter-
mined by the values set by the A and B SWEEP TIME/DIV
controls.
1.
Apply a signal to the INPUT jack and set the vertical
MODE to the channel to be used, adjusting VOLTS/DIV
for an easily observed display of the waveform and the
other controls if necessary.
. Set the
A SWEEP TIME/DIV so that several cycles of the
waveform are displayed. Depress the HOLD OFF control
to (AFTER DELAY).
When the HORIZ MODE is set to INT, the magnified por-
tion of the waveform will appeared intensified on the CRT
display.
. Use the DELAY TIME MULT to shift the intensified por-
tion of waveform to correspond with the section to be
magnified for observation. Use the
B SWEEP TIME/DIV
to adjust intensified portion to cover the entire portion
to be magnified.
. Set the HORIZ MODE to either ALT or B and use the =
POSITION and TRACE SEPARATION controls to adjust
the display for easy viewing.
. Time measurements are performed in the same manner
from the B sweep as was described above for A sweep
time measurements.
The apparent magnification of the intensified waveform
section is the A SWEEP
TIME/DIV
divided by the B
SWEEP TIME/DIV.
Using the formula:
The apparent magnification
|_| A SWEEP TIME/DIV setting
of the intensified waveform _
B SWEEP TIME/DIV setting
Perr
lide |
- phot
nk 4
is
[EXAMPLE]
In the example, the
A SWEEP TIME is 2 us and the
BSWEEP
TIME is 0.2 ws. (See Fig. 45)
Substituting the given value:
Apparent magnification ratio =
2x 10-6
0.2x 10-8
=10
32
With the above magnification, if the magnification ratio is
increased, delay jitter will occur.
To achieve a stable display, set the
B MODE to TRIG and
used the triggered mode of operation.
1.
2:
3.
Perform the above steps 1 through 3.
Pull the HOLD OFF control to activate B TRIG'D function.
Set the HORIZ MODE to either ALT or B. The apparent
magnification will be the same as described above.
15. APPLICATION
OF X-Y OPERATION
* Phase Shift Measurement
A method of phase measurement requires calculations bas-
ed on the Lissajous patterns obtained using X-Y operations.
Distortion due to non-linear amplification also can be dis-
played.
A sine wave input is applied to the audio circuit being test-
ed. The same sine wave input is applied to the vertical in-
put of the oscilloscope, and the output of the tested circuit
is applied to the horizontal input of the oscilloscope. The
amount of phase difference between the two signals can
be calculated from the resulting waveform.
To make phase measurements, use the following procedure.
1
. Using an audio signal generator with a pure sinusoidal
signal, apply a sine wave test signal at the desired test
frequency to the audio network being tested.
. Set the signal generator output for the normal operating
level of the circuit being tested. If desired, the circuit's
output may be observed on the oscilloscope. If the test
circuit is overdriven, the sine wave display on the oscil-
loscope is clipped and the signal level must be reduced.
. Connect the channel 2 probe to the output of the test
circuit.
. Select X-Y operation by placing the TRIG MODE switch
in the X-Y position.
. Connect the channel
1 probe to the input of the test
circuit.
(The input and output test connections to the vertical and
horizontal oscilloscope inputs may be reserved.)
. Adjust the channel 1 and 2 gain controls jor a suitable
viewing size.
. Some typical results are shown in Fig. 47.
If the two signals are in phase, the oscilloscope trace is
a straight diagonal line. If the vertical and horizontal gain
are properly adjusted, this line is at a 45° angle.
A 90°
phase shift produces a circular oscilloscope pattern.
Phase shift of less (or more) than 90° prods ces an ellip-
tical oscilloscope pattern. The amount of phease shift can
be calculated from the oscilloscope trace as sfhown in Fig.
57.
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